The major ethnic groups in the United States, African-Americans, Latinos, and Asians, show distinctive patterns of pregnancy outcome, including preterm birth, low birth weight, and infant mortality. Numerous reports have described this, but there has been little effort to extend these observations to address possible causal pathways underlying the patterns. In order to extend our understanding of the role of ethnicity and socioeconomic conditions on pregnancy outcome, we propose to analyze births in New York City over the period 1998-2002, a 5-year period straddling the 2000 Census, with over 500,000 births included in the final analysis. Through this combination of data sources, we will: describe ethnic patterns of pregnancy outcome, including preterm birth, growth restriction, and common pregnancy complications, characterize risk factors among women of varying ethnicity, including sociodemographic characteristics such as age, marital status, and education, and a number of medical conditions affecting the outcome of pregnancy. Measures of ethnicity at the individual level include race, Hispanic ethnicity, nativity, and ancestry, and we will be able to identify and analyze refined subgroups (e.g., Puerto Ricans, Asian Indians, Koreans) given the size and diversity of the New York City population. We will conduct a multi-level statistical analysis that takes into account both individual attributes from the birth certificate and neighborhood features from the US Census to examine their separate and joint effects, focusing on the influence of ethnicity, socioeconomic status, nativity, and concentration of ethnicity within Census Tracts. By elucidating the relationship between ethnicity and pregnancy outcome more fully, considering a broader range of ethnicities defined in greater detail, and integrating individual and community level socioeconomic influences, we will be better able to target groups in need of intervention as well as identify clues to etiology.